Some circuits may use a bidirectional bus to transmit and receive data to and from another circuit. In such a circuit, a master device and a slave device may be connected via a bidirectional bus, and the master device may control the direction of data transmission and reception.
In this case, the master device inputs a bidirectional-bus control signal to the slave device to control the direction of data transmission and reception between the master device and the slave device. The relationship of the direction of data transmission and reception between the master device and the slave device may be the relationship in which the master device and the slave device are a transmitting side and a receiving side, respectively, or the master device and the slave device are a receiving side and a transmitting side, respectively.
On the other hand, when the bidirectional-bus control signal is inverted owing to some malfunction and, for example, both of the master device and slave device become transmitting sides, a bus fight may occur in which outputs collide on the bus. When a bus fight occurs, an element therein may be damaged, which may cause a failure in the device or devices. For example, when both of the master device and slave device become receiving sides, the bus has an intermediate potential state. At the intermediate potential state, the elements in the master device and slave device become instable, which may cause a failure in the device or devices.    [Patent Document 1] Japanese Laid-open Patent Publication No. 58-024925    [Patent Document 2] Japanese Laid-open Patent Publication No. 09-054752